Understanding a Thermostatic Expansion Valve

A throttling device that is used by both refrigeration and air conditioning, a thermostatic expansion valve is designed to control the amount of refrigerant that enters your system’s evaporator. This amount is determined by the temperature and pressure of the evaporator outlet.

The Different Phases of the Process

There are different phases and amounts of pressure that the refrigerant will exist at as it makes its way through your system. It starts off by going through the evaporator. From there, it travels through the compressor, the condenser, and the throttling device. The refrigerant is then injected in liquid form through the evaporator and compressor.

Parts and Operation

There are different versions of a thermostatic expansion valve, but they generally have the same parts in common. The most basic components of the valve include a diaphragm, power source, setting spring, and orifice.

When it comes to the operation of the valve, there are three forms of pressure in play. The bulb pressure, spring pressure, and evaporator pressure are working throughout the process. Bulb pressure comes from a bulb that is located at the end of the evaporator. As this bulb assesses temperature, the diaphragm is moved accordingly. Spring pressure remains constant as it pushes up against the diaphragm to counteract the pressure at the bulb. Evaporator pressure is used to push the diaphragm upwards as suction increases. This pressure will be affected by things like room temperature.

Internal/External Equalization

The two main types of pressure equalization that are available with a thermostatic expansion valve are internal and external. An external pressure system is the most commonly used system, and it is used for multiple circuit systems. They’re designed to monitor large drops in pressure. The internal versions monitor the pressure that’s present at the valve’s outlet.

At New River Heating & Air, our technicians are available to answer any questions regarding the use of thermostatic expansion valves. In Radford, Virginia, and surrounding areas, New River Heating & Air also installs, repairs, and maintains heating and cooling systems. Our team provides indoor air quality and duct cleaning services as well. Contact us today for more information.